The present invention relates to an imaging apparatus used as a digital camera, a digital video camera, or the like, and in particular relates to an imaging apparatus suitable for an in-vehicle camera.
An imaging apparatus having an optical element such as a lens for imaging or the like, and an image sensor such as a CCD (Charge-Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) or the like is widely used in an in-vehicle camera, a digital camera, a digital video camera or the like.
In the above imaging apparatus, normally, at an image forming position of an optical element, an image sensor is fixed in a state where a high-accuracy positioning adjustment has been performed, and the optical element and the image sensor are stored in a case body. And in some cases, the optical element and the case body are integrated. The case body has a waterproof function and a dustproof function.
On the other hand, as for an in-vehicle camera or the like, depending on usages, there is a case where models of which the external shapes are similar but specifications of lenses and image sensors are slightly different are needed. For example, even though the same lens can be used, in the case of an analog output and in the case of a digital output, there is a case where different kinds of image sensors have to be used. And there are cases such that in a case where a high-accuracy image is needed, an image sensor having pixels in a small size is used, and in the case of using in a dark place, an image sensor having pixels in a large size and a high imaging sensitivity is used. In these cases, even though the same lens can be used, there is a case where different kinds of image sensors have to be used.
And even in the case of using the same image sensor, there is a case where different lenses are needed. For example, in a case where an in-vehicle camera is used for a rear-view monitor, it is preferable that a horizontal angle of view (visible range) be wider, and in a case where an in-vehicle camera is used for an obstacle detection, it is preferable that a particular range look larger. In this case, different lenses are used for the same image sensor (there is a case where an electrical component system is included.)
Incidentally, as a conventional imaging apparatus, an imaging apparatus has been proposed in which a case body is divided into a front case and a rear case, and in the front case a lens, a lens barrel and an image sensor are arranged such that each optical axis corresponds, and an O-ring interposes between the front case and the rear case, and thereby the degree of freedom in positioning of the image sensor for the lens is ensured and waterproof and dustproof functions of the apparatus are improved (see Japanese patent application publication number 2008-33010).
Additionally, an imaging apparatus has also been proposed which is configured such that a lens barrel holding a lens is integrally formed with a case body, and a circuit board having an image sensor is screwed to a screw of an inner circumferential surface of the case body, and in which a distance between the lens and the image sensor is adjustable by rotating the lens (or the circuit board) (see Japanese patent application publication number 2009-290527).
However, in the imaging apparatus disclosed in Japanese patent application publication number 2008-33010 of the above conventional imaging apparatuses, the following problem occurs when an image sensor where a thickness in the optical axis direction is different is mounted in the front case.
As types of an image sensor, a QFP (Quad Flat Package), which is thick and large, and a CSP (Chip Size Package), which is thin and small, are known. Here, when the QFP is arranged in a case body suitable for the CSP, a front case of the case body and a circuit board are too distant to bond the front case to the circuit board, because a distance between a pixel surface of the image sensor and the circuit board of the QFP is large. On the other hand, when the CSP is arranged in a case body suitable for the QFP, a front case of the case body and a circuit board are too close, and therefore the front case interferes with the circuit board, because a distance between a pixel surface of the image sensor and the circuit board of the CSP is small.
In order to avoid such a problem, a suitable form of a case body for a form of an image sensor is required. However, this causes a new problem such that a great number of components are needed. And additionally, a lens barrel is needed to be molded with high accuracy in order to hold a lens, and in some cases, it is needed to be molded with an accuracy of approximately a few μm. It is very difficult to manufacture a lens barrel with such accuracy, and in addition there is a case where a difference in form occurs. In that case, assembly accuracy of the lens is deteriorated, and even in a case where an assembled lens group has the same lens constitution, an optical characteristic is different.
If a lens barrel is only manufactured with high accuracy, manufacture of the lens barrel by cutting aluminum or the like is considered. However, it is not preferable to manufacture a constitution of the lens barrel including a bonded part by cutting aluminum from the viewpoint of mass production performance. This is because secondary processing is needed, even in the case of die-casting, in order to manufacture a form of the bonded part with high accuracy.
Additionally, in the imaging apparatus disclosed in Japanese patent application publication number 2009-290527, a movable range of the image sensor is wide, and if a thickness of the image sensor in the optical axis direction is changed, there is no problem in adjusting the distance between the lens and the image sensor. However, in a constitution disclosed in Japanese patent application publication number 2009-290527, the distance between the lens and the image sensor is adjusted by rotating the image sensor (or the lens). Therefore, in a case where a case body of a lens barrel holding the lens is a quadrangle in a cross-section perpendicular to the optical axis, four sides of the image sensor and four sides of the case body do not always correspond, and an arrangement direction of the case body is limited. In the imaging apparatus disclosed in Japanese patent application publication number 2009-290527, in order to avoid this, the case body where the lens is stored is limited to a circular cylinder shape.